Alternating current motor



y 1932'- E. L. BARRETT 1,858,571-

ALTERNATING CURRENT MOTOR Filed April 11, 1929 I as Patented May 17, 1932 UNITED STATES PATENT OFFICE EDWARD L. BARRETT, OI CHICAGO, ILLINOIS, ASSIGNOR TO UTAH RADIO PROIDUUI'B CO OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS ALTEBNATING CURRENT MOTOR Application filed April 11, 1929.. Serial No. 354,198.

to induce a rotating magneticfield, certain of which difier from others by being oppositely shaded, so that upon energization of one series of like shaded poles the induced magnetic field will rotate in one direction, and energization of the other series of poles creates a magnetic field rotating in the opposite direction.

In connection with the foregoing object,

.- the invention also contemplates the provision of means on the magnetic field structure by which indirect energization of the unenergized poles by the energized poles is prevented.

Other objects and advanta es will become apparent in the following escription and from the accompanying drawings, in which:

Figure 1 is a transverse elevation partially in section showing an end face view of the magnetic field structure and rotor.

' Fig. 2 is a diagrammatic illustration of the motor circuits.

In accomplishing the objects of the invention, the fact that the shading of certain portions of the poles of the magnetic field structure causes a progressive rotating shift in the magnetic field from the unshaded to theshaded portion of the poles is utilized to eifect rotation of the armature or rotor in the same direction as the shift in the field. Therefore, by providing a plurality of pairs of oppositely disposed poles surrounding the rotor, certain of which pairs are shaded on one side for inducing a rotation of the rotor in one' direction while the remaining sets of pole pieces are oppositely shaded to induce a rotation of the rotor in an opposite direction, and by further providing means for selectively energizing one or the other of said sets of poles, rotation of the rotor in one direction or the other may be produced.

In the drawings the features of the invention have been illustrated as being embodied in an induction motor of the single phase type. Thus, 10 designates generally an armature or rotor of the squirrel cage type mounted in any suitable manner upon an armature shaft 11 for rotational movement. Surrounding the rotor is a magnetic field structure or stator 12 built up in the usual manner in the form of a laminated structure secured together by means of bolts 13, or the like.

In the common construction of a motor of this type, two or more pole units, formed as an integral part of the magnetic field structure, are arranged to be excited by a coil or other suitable winding connected to a source of alternating current. In the resent embodiment four poles 14, 15, 16 an 17, are shown spaced equidistantly about the stator and the diametrically opposed poles 14, 16 and 15, 17 comprise the sets of poles forming the pole units. In consequence, the motor illustrated is of the type known as a two pole motor, inasmuch as at any time onl two of the four poles will be energized. 1 1 is contemplated, however, that additional pole units may be provided if desired.

The active face of each of the poles is divided into two sections, as by means of a transverse slot or recess 18 positioned relatively near one side of the face, thus dividing the face into sections of unequal face area.

'Each of the pole sections of smaller area,

designated 14*, 15, 16, 17, respectively, constitute the shaded section of the pole and are arranged to receive a permanently closed, short-circuiting, shading ring 19 which ma be in the form of a centrall apertured dis or slug of cop er, or similar y good conducting material. 11 order to increase the area of the active face of the unshaded pole sections lateral extensions, or 1:065, 14', 15", 16 an 17, respectively, are formed on each of the poles, and extend from the side thereof opposite the shaded sections.

It will be observed that the poles of one pole unit are shaded to induce rotation of the rotor in the same direction, but that the poles of the other pole unit are oppositel shaded That is to sa the poles 14 and 16 are shaded upon the rig t hand side (looking at the active face thereof) while the poles 15 and 17 are shaded on the left hand side. Consequently, the poles 14 and 16, when energ1zed, will induce rotation of the rotor 10 in a clock wise direction, and the energizati on of the poles 15 and 17 will induce rotation of the rotor in a counter-clockwise direction.

Each of the poles which induce rotation in the same direction, as for example the oles 14 and 16, is adapted to be energize by means of a coil or other suitable winding 20, which coils are connected in series and are reversed with respect to each other in the customary manner. Similarly, a second pair of coils 21, connected and reversed in the same manner, surround the pole pieces 15 and 17. This arrangement of ener 'zing co1ls 1s more clearly appprent in the 1agrammat1c illustration o i 2.

Suitable leads 22, 23 for the coils 20, and 24, 25 for the coils 21 are provided for connecting the respective coils with a source of alternating current (not shown). If desired, one of the leads from each set of cells, as for example, the leads 22 and 25. may be connected to a common lead 26. It will be readily seen, therefore, that by establishing a circuit through the leads 28, 26 the cells 20 will be energized to induce rotation of the rotor in a clockwise direction, while, on the other hand, a circuit established through the leads 24, 26 energizes the coils 21 to induce rotation in a counterclockwise directlon.

For the purpose of establishing these circuitsany suitable type of selector switch, as indicated at 28, may be provided.

It is contemplated that a motor embodying the structural elements heretofore described might be of relatively low efliciency due to the fact that part of the flux flowing between the energized poles across the space occupied by the rotor W111 (probably be shorted through the interme iate unenergized oles. Consequently, an induced flux mi ht e created in the unenergizedpoles which, since these poles induce rotation in a direction op osite from the direction of rotation induce by the energized poles, would have an o posing efi'ect tending to decrease materia ly the efliciency of the motor. It has been found, however, that by providing means, intermediate and se arating each pole from the next adjacent po 0 to interce t that part of the flux which otherwise miglit flow into the unenergized poles, any induced oppelsing flux may be substantially eliminatna e To this end the stator is provided with a plurality of integrally formed inwardly extending members 27 which are spaced from and are positioned between adjacent poles. The members 27 are substantially the full width of the stator and the face thereof is positioned adjacent the rotor as in the case of the energized poles. It may be said that the members 27 constitute dunmiy poles inasmuch as they are not provided with windings or other energizing meansand serve merely to provide a short circuit or ath which may be traversed by a part of the magnetic flux flowing out of the energized oles. Hence, any portion of the magnetic ux which does not flow directly between the energized poles will flow from the energized poles to the adjacent shortin members 27, instead of to the unenergize poles thereby preventing an induced op osing flux from bem set up in the unenergized oles. Althoug the invention is susceptib e of various modifications and alternative constructions, I have shown and herein described in detail the preferred embodiment but it is to be understood that I do not thereby intend to limit the invention to the specific form disclosed but intend to cover all modifications and alternative constructions falling within the s irit and scope of the invention as expresse in the appended claims.

I claim as my invention: 1. In a device of the character described, a ma netic field structure having a plurality of po es thereon, shading means on certain of said poles for inducing a magnetic field constantly rotating in one direction when said poles are energized, shading means on others of said poles for inducing a magnetic field constantly rotating in the otpposite direction when said last mentione poles are energized, means interposed between each of said poles for interrupting a flow of magnetic flux between adjacent poles, and means for selectively energizing one or the other groups of said like shaded poles.

2. An alternating current motor comprising, in combination, a rotor, and means for in ucing rotation of said rotor in one direction or the other including poles permanently shaded to induce rotation of said rotor in one direction, other poles permanently and oppositely shaded to induce rotation of said rotor in the opposite direction, means for selectivel energizing the similarly shaded poles, an means for preventing the flow of ux from the energized poles to the unenergized poles.

Ill

3. An alternating current motor comprising, in combination, a rotor, a magnetic field structure for inducing rotation thereof, said structure having poles permanently shaded to induce rotation of the rotor in one direction, other poles on said structure permanently shaded to induce rotation of the rotor in the opposite direction, means for se arately and selectively energizing the hke shaded poles, and an unenergized pole on said structure separatin each shaded pole from the next adjacent s aded pole.

4. In an alternating current motor, a magnetic field structure comprising a plurality of pole units, permanently short-circuited shading means on certain of said units to induce a magnetic field rotating in one direction, permanently short-circuited shading means on other units to induce a magnetic field rotating in the opposite direction, energizing windings on said units for energizing one or the other groups of the similarly shaded units, and unenergized poles interposed between the oppositely shaded pole units. 4

5. In a' reversible alternating current motor, a magnetic field'structure having poles permanently shaded to induce a magnetic field rotating in one direction and having other poles permanently and oppositely shaded to induce a magnetic field rotating in the opposite direction, means for selectively energizing one or the other groups of like shaded poles, and means for preventing induced energization of the unenergized group of poles from any of the energized poles including means interposed between oppositely shaded poles for interrupting a flow of magnetic flux between energlzed and unenergized poles. In testimony whereof, I have hereunto affixe'd my signature.

' EDWARD L. BARRETT. 

